Design changes after permissions granted

We're getting close to finalising our house design in the Fermo region and I'm wondering what sort of changes can be made to the design once permissions have been granted - and at what cost. I'm pretty sure the footprint won't change - but for example, could we move the position of some windows, swap a window for a french door, change the internal layout etc once the comune have granted permission to build? If we could make changes - I'd be surprised if it was free - does anyone have an idea how much variations are likely to cost?I'm a bit sceptical of the italians locally who keep saying no problem no problem ... as in my experience there is usually a cost attached somewhere along the line!Grateful for any tipsBrancusi